1. Field of the Invention
The present invention relates generally to flexible piping, and in particular to multi-layered flexible piping with an insulating layer or layers.
2. Description of the Related Art
Flexible piping is utilized in a variety of applications. For example, flexible piping or hose can be used for conveying various fluids, such as exhaust gases from internal combustion engines in vehicles and other equipment, for ventilation, for fuel hose such as on gas grills, and for lining chimneys and flues. Flexible piping or hose can also be used for conveying bulk materials, such as dust, pellets, grain, etc. One type of flexible piping can be formed by spiral-winding material bands or windings on a pipe winding machine. Previous types of pipe winding machines have used hook-shaped band guides and rotating mandrels for spiral-winding flexible piping. For example, the McGowen U.S. Pat. No. 4,197,728 discloses a pipe winding machine with a rotating mandrel for receiving bands from a series of profiling rollers which shape the bands for interlocking engagement on the mandrel. Piping formed in this manner is flexible because the interlocking connection of the band edges permits limited axial slippage between adjacent bands.
Another type of pipe winding machine uses profiling rollers for imparting a convoluted cross-sectional configuration to a continuous length of band material. The band edges are interlocked by knurling wheels with this type of machine. Piping flexibility is provided by the convolutions of the band, which permit axial compression and expansion.
An advantage of having piping sections formed by spiral-winding is that they can be formed to practically any length and with various diameters. However, forming a fluid-tight seal between the interlocking, spiral-wound bands can be difficult, particularly since the interlocking bands often have sliding metal-to-metal contact areas which can pass fluid.
In many flexible piping applications it may be desirable to insulate the flexible piping. Such insulation can provide thermal, moisture and corrosion protection and control. For example, a layer of insulation may be desirable for providing a vapor barrier to control exposure of the flexible piping to moisture. Insulation may also be desirable to achieve fluid-tightness with flexible piping which conducts exhaust fumes or other fluids with undesirable (e.g., toxic) properties, and to contain such fluids within a fluid-handling system including insulated flexible piping to protect persons, property and the environment from exposure to such undesirable and potentially harmful fluids.
Heretofore there has not been available flexible piping, a method of producing same or a machine for producing same, with the advantages and features of the present invention.